Why is ADHD so difficult to diagnose in older adults?

KEYWORDS:

• ADHD
• Attention Deficit Hyperactivity Disorder
• Older adults
• Cognitive decline
• Geriatrics

1. Introduction

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental condition characterized by inappropriate levels of inattention, hyperactivity, and impulsivity, which manifest in various environments [1]. Longitudinal studies show that 60% to 90% of children with ADHD continue to exhibit symptoms and impairments into adulthood [2,3]. Meta-analysis finds the prevalence of ADHD in older adults to be 2.5% [4]. The validity of ADHD in adults and its ongoing impact in adulthood have been substantiated by genetic studies [5] and in longitudinal studies tracking individuals from childhood into adulthood [6,7]. However, because longitudinal studies have not followed children past their forties and cross-sectional studies rarely investigate ADHD in adults older than 50, researchers and clinicians are left to speculate about the most appropriate diagnostic approaches for this particular demographic population. However, gaining insight into this topic is crucial, as the population of individuals aged over 65 will nearly double from 43.1 million in 2012 to 88.5 million by 2050 in the United States [8].

So, what do we know about ADHD in older adults? Dobrosavljevic et al. analyzed 20 studies across 32 databases, with a total sample size of 20,999,871 individuals, of which 41,420 had ADHD [6]. The estimated prevalence of ADHD in the elderly was 2.18% (95% CI = 1.51, 3.16) when diagnosed through validated scales in community samples and 0.23% (95% CI = 0.06, 0.15) when relying on clinical diagnoses in electronic health records. The underdiagnosis of ADHD in medical records underscores the need for ongoing education among clinicians treating older patients. Equally, worrisome was the low prevalence of treatment for ADHD in the elderly: 0.09% (95% CI = 0.12, 0.43), which is less than 40% of those clinically diagnosed with ADHD.

Although DSM 5 modestly revised its diagnostic criteria to address adult ADHD presentations, the symptoms of ADHD continue to be those derived from studies of youth. Clinicians have adjusted these criteria to accommodate adult manifestations, including those in individuals over 50 years old. Barkley and Murphy’s screening tool was validated in adults aged 60–94 years old against a clinical-research interview [9,10] Their tool comprises seven executive function items and two DSM-IV-TR symptom criteria. The screening tool had a sensitivity of 0.80 and a specificity of 0.77 but test-retest reliability was moderate (intraclass correlation = 0.56), suggesting a need for further refinement.

Regarding management strategies, there is a paucity of pharmacologic research using ADHD medications in patients over age 60. Pharmacologic trials for ADHD in adults excluded those older than 55 for lisdexamfetamine [11] and 65 for mixed amphetamine salts XR [12], OROS methylphenidate [13], dexmethylphenidate XR [14], atomoxetine [15] and viloxazine [16]. The sample sizes over the age of 50 in the adult trials have not been noted in the publications. Ermer et al. (2013) assessed safety parameters for lisdexamfetamine in subjects ages 55–84 [17]. Although the authors concluded that no trends in pulse and blood pressure with lisdexamfetamine were seen by age, for a minority of adults, stimulant treatment will elevate blood pressure levels that warrant clinical action. It should be kept in mind that ADHD has been demonstrated to be an independent risk factor for cardiovascular disease, and the hazard ratio is higher in younger adults (HR-2.49; ages 18–30) than older adults (HR- 1.22; ages 61–73) [18] This safety literature is not widely known among clinicians prescribing these medications to older adults.

2. Clinical perspectives

2.1. Clinical blindness

Because professional training programs in fields such as psychiatry, psychology, nursing, mental health, and primary care have paid scant attention to adult ADHD, clinicians lack the skills needed to identify, diagnose, and treat ADHD in older patients. ‘If it is so important, why did I not receive training?’ Moreover, some clinicians dismiss the diagnosis as a passing trend aimed at unnecessarily increasing medication prescriptions. Overcoming such a clinical perspective requires educating and training well-intentioned clinicians dedicated to providing optimal care for their patients.

2.2. Clinical prejudice

Some clinicians think, ‘Why bother treating it? They’ve coped with it their entire lives.’ Such a view does not acknowledge that the patient has come to treatment because their lifelong coping has led to many failed struggles with tasks and relationships. It underestimates the psychological, emotional, and financial toll of ADHD-related challenges throughout their lifespan. Without an ADHD diagnosis, individuals accept their difficulties as inherent to their identity, not recognizing that a disorder has hindered their potential. Effective treatment, leading to symptom reduction and improved functioning, enables individuals to differentiate between their identity (who they are) and their ADHD (what they have). This realization usually rejuvenates their self-image and confidence.

Clinical prejudice is further evident in statements like, ‘I won’t prescribe ADHD medications to a patient of this age, regardless of the diagnosis’ which stem from concerns about medical risks associated with these medications. Older patients often have preexisting medical conditions and may be taking multiple medications concurrently [7,19]. Assessing the risk versus benefit of ADHD medications in the context of these medical factors is intricate. Cardiac issues are a primary concern, prompting ongoing publications reviewing the literature [20]. It’s important to note that ADHD medications can lead to increases in blood pressure and/or heart rate, which necessitate careful monitoring and treatment if necessary. Ultimately, the decision to treat older adults with ADHD medications involves balancing the potential improvement in quality of life, which is often substantial, against manageable medical risks. While this exercise is intellectual in nature, actual treatment experiences can refine the risk-benefit analysis for clinicians and patients.

2.3. Clinical inexperience

Some clinicians who acknowledge the validity of ADHD in older adults and the benefits of treatment lack clinical experience, which breeds uncertainty. Questions arise: What does the assessment entail? Which symptoms should I be looking for? What other conditions should I consider in my differential diagnosis? How do I differentiate between cognitive symptoms stemming from ADHD versus those from other medical or psychological causes? And where do age-related cognitive changes, mild cognitive impairment, and dementia factor into my clinical diagnoses? Even if confident in the diagnosis, prescribing ADHD medications may still pose a challenge because medication dosing is unfamiliar. For the untrained or inadequately informed clinician, these uncertainties can lead to anxiety-induced indecision and deferral of treatment.

2.4. Diagnostic challenges

Diagnosing ADHD in older adults with cognitive complaints is intricate due to the differential diagnoses that must be considered [21]. The clinical complexity lies in navigating the diagnostic process for these differential diagnoses, which can be broadly categorized into medical, psychiatric, and psychological factors, each further divided into chronic and acute subcategories. Acute medical conditions such as traumatic brain injury or chemotherapy along with chronic medical issues that cause cognitive symptoms due to medications (e.g. topiramate) or conditions such as Ehlers-Danlos Syndrome, which is associated with cognitive impairments [22]. For psychiatric conditions contributing to cognitive symptoms, acute disorders might manifest as a major depressive episode, whereas chronic psychiatric issues could include treatment-resistant major depression that persists for months and years. Substance use disorders could present as an acute or chronic condition negatively impacting cognitive function.

Psychological experiences of anxious and/or depressive symptoms without meeting diagnostic thresholds for disorders will diminish cognitive performance [23]. Acute changes in cognition and behavior might stem from psychologically traumatic events (e.g. sexual assault), while chronic influences could arise from longstanding stressors (e.g. ongoing conflict with a supervisor) perpetuating chronic anxiety.

Using a differential diagnosis decision tree incorporating these medical, psychiatric, and psychological issues aids in discerning presenting symptoms and considering the relevance of temporal symptom trajectories in the diagnostic process. It’s crucial to note that ADHD is a disorder with roots firmly established in childhood or early adolescence, and its symptoms and impairments often persist throughout one’s lifespan.

2.5. Clinical complexity

While the array of presenting symptoms necessitates consideration of differential diagnoses, clinical conclusions are seldom binary – often involving the possibility of contemporaneous processes. The presence of concurrent disorders that both manifest cognitive symptoms adds further complexity to the diagnostic assessments. Consider, for example, the co-occurrence of a neurologic disorder (mild cognitive impairment) with ADHD. Concurrence has an additive effect on cognitive symptoms. The same issue of disorder concurrence may occur with psychiatric illnesses. In older adults, the complexity of psychiatric disorder's effect on cognition is compounded by concurrent medical conditions. Additionally, statistics indicate that two-thirds of individuals over 65 are prescribed at least three medications [24].

This raises many questions for clinicians: How does one differentiate between cognitive symptoms of depression and similar symptoms of ADHD in an older adult? Could medications prescribed for other conditions be exacerbating cognitive symptoms associated with ADHD? Might post-traumatic stress disorder exacerbate cognitive complaints in individuals with ADHD?

The presence of concurrent disorders presenting with cognitive symptoms complicates the clinical picture, blurring the distinction between symptoms attributable to different conditions. The objective is to identify concurrent disorders, isolate those that do not impact cognition, and then prioritize the remaining disorders based on their likelihood of contributing to cognitive symptoms. Clinical features that distinguish ADHD symptoms from other concurrent disorders are stable chronicity vs variability of symptoms, age of onset (ADHD in childhood), temporal relationship to an event (traumatic brain injury, an infection, or new medication), quality of cognitive symptoms (word finding/misspelling found in MCI, not ADHD). After clarifying and prioritizing diagnoses, clinicians can develop a comprehensive individualized treatment plan and pharmacological algorithm.

2.6. Treatment hesitancy

Many clinicians hesitate to prescribe ADHD medications to older patients due to increased medical risks associated with aging, such as heart conditions, interactions with other medications they are taking, and safety issues specific to this age group. Historically, physicians were taught that psychostimulants were prone to abuse, addiction, and hypertension. However, the therapeutic use of psychostimulants infrequently leads to addiction, and while misuse and diversion can happen, it is uncommon among older adults [25].

Furthermore, even thoughtful, well-trained clinicians may hesitate to introduce a stimulant, fearing it could compromise the patient’s medical stability (e.g. post-myocardial infarction, post-stroke, fragile hypertension, and atrial fibrillation). As recently pointed out [20] ADHD medications have been shown to induce in general small increased values of blood pressure but not more serious cardiovascular events, even though this evidence needs to be replicated in older patients. Overall, potential cardiovascular risks should be balanced against established benefits. Patients with known cardiac illnesses need to be assessed for the appropriateness of an ADHD medication, likely in consultation with a primary care provider and/or cardiologist. While international guidelines for ADHD do not recommend routine echocardiograms in children or adults, it’s important to recognize that these recommendations were not based on information about older adults with or without cardiac illness [26–28].

Treatment challenges are real but should not paralyze the clinical care of older adults with ADHD. One must balance the risk of medical complications against the potential benefits of reducing ADHD symptoms, minimizing impairments, and improving overall quality of life.

3. Conclusion

Clinicians need to be aware of biases that arise during the assessment, diagnosis, and treatment of older adults with ADHD that may interfere with creating an effective comprehensive treatment plan, balancing medical risks against the benefits of symptom management to improve the quality of life for older adults with ADHD. ADHD is an impairing disorder that affects people of all ages but is frequently unidentified or ignored among older adults. Current diagnostic criteria remain based on studies of youth, calling for refined assessment tools for older adults. Pharmacological research for ADHD in patients over 60 is scant but suggests, along with clinical experience, that older adults experience the same efficacy and adverse effect profile as younger adults. While the research literature for this patient population is growing, there remain knowledge gaps in clinical care guidance and education that will require further attention.

4. Expert opinion

This editorial concludes that ADHD in older adults is poorly understood and under-recognized because of a lack of research, inadequate professional training of clinical providers, biases by clinicians in the assessment, diagnosis, and treatment, and hesitancy and prejudice in prescribing stimulant medications. Only a small fraction of older patients with cognitive complaints are evaluated for preexisting ADHD as a possible explanation for cognitive deficits. Ascribing cognitive deficits in these patients to age-related cognitive decline or mild cognitive impairment (MCI) denies them appropriate and effective treatment options. Correctly diagnosing ADHD in these patients provides them with an opportunity for effective treatment that will diminish cognitive symptoms, other symptoms of ADHD, and serious functional impairments. Such treatment typically improves the quality of life for years to come. Given the large population of older adults, this is fertile ground for much-needed research to address an aging population who would be better able to maintain a higher level of function and quality of life. We anticipate that further recognition and training of ADHD and older adults will result in more accurate diagnoses and the provision of effective treatments by clinicians who recognize the benefits. Clinical biases and fears about prescribing stimulant medications would be diminished with more patient care experience. The prescription of ADHD medications must consider the medical illnesses that accompany this aging population so that prescriptions are offered with an understanding of safety and risk. We hope that dedicated funding from governmental and non-governmental funding agencies will continue to increase the body of evidence able to inform clinical practice in this overlooked but highly relevant population.

Declaration of interest

Over the past 36 months, DW Goodman has served as a consultant to Takeda, Otsuka, Sunovion, Supernus, Noven, OnDosis, and Ironshore. He has received continuing education support, honorarium, and/or travel expenses for CME lectures delivered at the Neuroscience Education Institute, Medscape, American Professional Society for ADHD and Related Disorders, University of California-Riverside, University of Cincinnati. Samuele Cortese, who is an National Institute for Health and Care Research (NIHR) Research Professor (NIHR303122), is funded by the NIHR for this research project. S Cortese is also supported by NIHR grants NIHR203684, NIHR203035, NIHR130077, NIHR128472, RP-PG-0618–20003 and by grant 101,095,568-HORIZONHLTH- 2022-DISEASE-07-03 from the European Research Executive Agency. Additionally, he declares reimbursement for travel and accommodation expenses from the Association for Child and Adolescent Central Health (ACAMH) in relation to lectures delivered for ACAMH, the Canadian AADHD Alliance Resource, the British Association of Psychopharmacology, and by the Healthcare Convention for educational activity on ADHD, and he received honoraria from Medice. SV Faraone has received income, potential income, travel expenses, continuing education support, and/or research support from Aardvark, Aardwolf, AIMH, Akili, Arbor, Atentiv, Axsome, Genomind, Ironshore, Johnson & Johnson/Kenvue, Kanjo, KemPharm/Corium, Medice, Noven, Ondosis, Otsuka, Rhodes, Sky Therapeutics, Sandoz, Supernus, Tris, and Vallon. With his institution, he has US patent US20130217707 A1 for the use of sodium-hydrogen exchange inhibitors in the treatment of ADHD. He also receives royalties from books published by Guilford Press: Straight Talk about Your Child’s Mental Health, Oxford University Press: Schizophrenia: The Facts and Elsevier: ADHD: Non-Pharmacologic Interventions. He is Program Director of www.ADHDEvidence.org and www.ADHDinAdults.com. Dr Faraone’s research and education programs are supported by: the European Union’s Horizon 2020 research and innovation programme under grant agreement 965,381, the NIH/National Institute of Mental Health (NIMH) via grants U01AR076092, U01AR076092-01A1, R0MH116037, 5R01AG064955–02, 1R21MH126494–01, 1R01NS128535–01, R01MH131685–01, 1R01MH130899-01A1, and U01MH135970, the Upstate Foundation, Corium Pharmaceuticals, Tris Pharmaceuticals, and Supernus Pharmaceutical Company. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Acknowledgments

The authors thank R Brown of the ADHDWorldFoundation.org for her administrative work on this manuscript. The views expressed in this publication are those of the author(s) and not necessarily those of the NIHR, NHS, or the UK Department of Health and Social Care.

Additional information

Funding

This paper was not funded.